1. Field of the Invention
The present invention relates to a liquid propellant rocket motor. More particularly, but not by way of limitation, the present invention relates to a rocket motor which is capable of very long run times without degradation or self destruction.
2. Background of the Invention
Generally speaking, liquid propellant rocket motors are well known in the art but are subject to constant evolution and improvement. In such motors, liquid fuel is typically combusted in the presence of an oxidizer. Hot exhaust gases are discharged through a nozzle to generate thrust. While there are any number of fuel and oxidizer combinations, kerosene and alcohol are common fuels and oxygen, stored in compressed liquid form, and nitrous oxide are common oxidizers.
As will be appreciated by those familiar with rocket motor architecture, the inner chamber of a rocket motor is subjected to high temperatures, relatively high pressure, and potentially, an abundance of oxygen, a combination which leads to erosion or consumption of the inside surfaces and weakening of the walls of the motor. Even with well  designed motors, these conditions set a maximum operating life of the motor, often measured in seconds, and, in a poorly designed motor, these conditions often lead to catastrophic failure.
Techniques have been developed to protect the motor from such degradation or self-destruction, but there are limitations or problems associated with these solutions. For example, it is well known to coat the inside of the engine with an ablative liner. Typically, an ablative liner is laminated to the inside surface of the motor housing. The liner insulates the wall to prevent failure of the motor and is designed to ablate, either through erosion, sublimation, or melting, at a rate which provides protection over the expected burn time of the engine. As the liner ablates, the hot ablated material is ejected from the engine by the exhaust gases, thus expelling the hottest wall material from the engine. While ablative liners are relatively inexpensive, they have a fairly short operating life and are consumed during use.
Another example of engine architecture employed to protect the rocket motor from self-destruction is regenerative cooling. In a regeneratively cooled rocket motor, outer shell of the rocket motor includes a spiral spacer sandwiched between an inner wall and an outer wall. Fuel is swirled down the walls of the motor before being injected into the motor. The result is that the wall is cooled by the fuel to prevent over heating and the subsequent damage. Regeneratively cooled motors are relatively complex and expensive. However, operating times for regenerative motors are often measured in minutes, rather than seconds. 
Yet another method of engine cooling is transpiration cooling. Transpiration cooling was first considered in late 1940's as a method of rocket motor cooling but early attempts were abandoned upon the successful development of a regeneratively cooled motor. Transpiration cooling, or sweat cooling, generally involves the injection of fluid or gas through a porous material placed between the motor wall and the combusting fuel. The porous material is cooled by the liquid fuel as it passes through.
Another area of concern with liquid propellant motors is ignition. If fuel and oxidizer collect in the chamber before ignition, the engine may experience a hard start, and possibly a resultant disassembly. In many cases, a rocket motor is ignited once and operates until its fuel and oxidizer stores are consumed. In such cases, motors are typically ignited by first igniting something which will ignite easily and burn furiously, i.e., a chunk of solid rocket fuel or the like. Obviously, this technique, the pyrotechnic ignitor, is impractical for applications where a motor will experience intermittent use, such as a thrustor for an orbiting craft or a steering thrustor.